Heating furnace



Mar. 3, 1925. f 1,528,333

' T. M. HUNTER ET AL f HEATING FURNACE Filed Jan, 18, 1922 Tr uw 1| i lul' I 7 Sheets-Sheet 1 T. M. HUNTER ET AL Mar. 3, 1925.

HEATING FURNACE Filed Jn.

18, 1922 '7 Sheeksr-Sheel. 2

nwe/woes THOMAS m HUA/75,6 gy CLAUDEH0L5LAG Mar. 3. 1925.

1,528,333 T. M. HUNTER ET AL HEATING-FURNACE 1922/4 '7 Sheets-Sheet 3 Filed Jan. 18,

.lul

| l'Il A TTURNEY Man 3', 1925. 1,528,333

' T. M. HUNTER ET AL.

HEATING FURNAQE Fil Jaln 18, 1922 `7 Sheets-Sheet 4 I a2 .3l

/Nvfnons 'moms M. HUNTER CLAUDE J. HOLSLAG Mar. 3, 1925.

T. M. HUNTER ET AL HEATING FURNACE Filed Jn. 18, 1922 7 Sheets-Sheet 6 ATTOHN Y Mar. 3. 1925.

T. M. HUNTER ET AL HEATING FURNACE Filed Jem. 18, 1922 '7 Sheefs-Sheet 7 ByCLAUDE u. HOLSl-AG ATTO/MIE Pateiited Mar. 3, 1.925.

UNITED STATES THoMAsM. HUNTER, or NEWARK, AND cLAunE J, HoLsLAe, or soUTH onAN'GE,

` 1,528,333 lPATENT OFFICE..

NEW JERSEY.

HEATINGv EURNAE.

Application led January 18, 1922. -Serial No. 539,085.

To all whom t concern.'

Be it known that We, THoMAsM. HUNTER and CLAUDE J. HoLsLAG, citizens of the ,United States, residing at Newark, in the specification.

Tl's invention relates to a heating furnace, particularly adapted for heating rivetsand the like, although it is to be thoroughly understood that our invention isyin no way limited to this particular use, even though it is illustrated -and described for this special purpose. VFurthermore, while we have chosen to illustrate certain forms of our invention utllizing an electric current either through electrodes forming an arc or through a suitable resistor, we wish it to be understood that', gas or liquid fuel may be used in place of either or both of the aforesaid means, as in certain localities, liquid fuel or gas may be oheaper'than electric current. f

kIn electric rivet heaters. with which we are familiar, the rivet is usually placed between a'pair of' electrodes serving as jaws for clamping the rivet vand thenpassing current through the rivet, thereby heating the'same. In order to get production with a rivet heater of'thisjkind, a'multiplicity of electrodes or jaws with theirattendant current serving means must be used, which adds weight andy cost to the apparatus. Furthermore 'these types of rivet heaters are open to Vother objections, one of which isl that they will not function properlywhen rusty rivets are used and it is to be remem- Y bered that rivets around a shipyard or railroad shop or other places of this kind are usually more-'or less rusty. Again the rivets, during a lchange in demand/ for the same, may become overheated or the demand may be greater thanthe capacity of the machine at hand, v and the riveters will be Vobliged to wait on the heater to supply the rivets. Also rivet heaters ofthis kind are usually not adapted to'take different sizes of rivets without making some change in the f rivet itself, or readjustment .of the jaws or change in the clamping jaws ofthe heater. It is the principal object of our invention to provide a furnace which overcomes these Figure 5 ,nace shown in to provide an extra amount of heat at the.

point of the furnace from which the rivets are withdrawn, yet we prefer to supply what might be `termed an auxiliary source of heat in order to maintain the rivetsI or other articles at the proper forging temperature.

Other and further objects will be apparent after a study of this specification and drawings annexed thereto.

The,drawings illustrating our invention Aare to be understood as being more or less diagrammatic in order to simplify them and still retain suiiicient of the structure to illustrate broadly how our invention may be utilized. In the drawings:

Figure 1 illustrates an' end view of one form of our furnace;

Figure 2 is a side viewofFigure 1; and l Figure :3 is a pla'n View of Figure 1, but" using a thirdelectrode.

Figure 4 illustrates another form of our invention; J

being a plan view of the same;

Figure 6 being a front view of Fig-4;

and

Figure 7 a view on Fig. 6.

Figure 8 Fig. 1; Figure 9 is a circuit diagram ,of the furnace shown in Figs. 4 to 7, inc. while Figure 10 'is a circuit diagram of lthe arrangement shown in Fig. 3.

Figure 11 is a side view of a modified form of our invention; d 'I Figure 12 being a p` an view of Figure 11; Figure 13 is a section on the line 13-13 of Fig. 12.

Figure 14 1s an end view of another form A of our invention showing more details than that illustrated in theprevious forms; Figure 15 isa plan view ofl Fig. 14; p Figure 16 is a view -on the line 16-#16 of'Fig. 14:;wl1ile4 l,

Figure Figure 17 is a view 'on the 1in@ 17-17 r18 is a fragmentaryI sectional view 9o is a circuit diagram of the furon the line 18-18 of ig. 16, showing the manner of holding and making connections to -one of the heating'units in the furnace; Figure 19.. is a circuit diagram of the furnace shown in Figs. 14 to 18, inc.

Figure 2() is a circuit diagram for the same furnace but using a separate source of current for the holding coil.

Figure 21 is an end View of a modified form of our invention; while f Figure 22 is a from; view. of Figure 21;'

Figure 23 is a top view of Figure 21; while f l Figure 24 isa sectionon the line'24-24 of Fig. 22.

Figure 25 is an end view of another modified form of our'invention;

Figure 26 being the front view of Fig. 25;

Figure 27 is a section on the line 27-27 of Fig. 25.

Figure-28 il`ustrates the manner of holding and carrying the current to the heating units as shown in Fi'g127.

Figures 29 to 32, inclusive, illustrate Wiring diagrams which may be used with the furnace shown in Figs. 25 to 28, inc.

Referring now to the details, wherein like numbers refer to 4corresponding parts-'in so far'aspossible', 1 illustrates the body portion .of a furnace which may be constructed of suitable lire brick and cementlwith any as a'stabilizer to the arc. "throughthclarc and the electrode 5 current .suitable frame to hold the fire brick and cement in position. The front lof body 1 has an opening 2 extending into the interior chamber 3. This opening '2 isx for thepurpose of inserting rivets or other .articles therethrough into the chamber 3. vCarried on the top of the furnace 1 is an electromagnetv 4, the function of which will be directly explained. Passing through the sides of the furnace are arc e'ectrodes 5 and 6, while in the lbottom of the furnace is a heating unit 7, an opening 8 is provided adjacent the l'bottom' of the furnace for the` purpose of withdrawing the rivets or other articles to be heated. It is to4 be understood that, suitable coverings are used over the openings 2 and 8, but .for the purpose of simplicity they are not shown in Figs. 1

and 2. The heatingunit 7 may or may not' be used. In Fig. 3, in addition to the electrodes 5 and 6, a 'third' electrode 9 is used where a three-wire system is utilized. The electrodev 9 may also be a dead electrode, the arc jumping from -5 to 9,v then to 6, thus making two arcs in series, which raises .the power voltage and decreases the reactance voltage, Athereby raising the power" factor.`

e operation .of the furnace will best be understood by a description of Fig. 8 wherein it is seen that the resistor 7 which may be of any suitable'character is connected to one of the arc electrodes 6. The resistor 7 acts After passing `Figs. 1 to 3, inc.

. for a f furnace shown in Fi up the chamber 3 and th'ework W, la point,v

probably close to the recalescent point of the work, is reached, Where'by therivets or work lose their magnetism and drop automatically to the bottom of the furnace ontop or in close proximity to the L op of :the stabilizing resistor 7, which it is seen performs `the double function of serving tov stabilize the arc as we'l as to act as a heaterfor Vmaintaining the rivets atth-eir proper forging temperature. By this arrangement it is seen that rivets of any length or diameter may beused proiiiiscuously for as soon" as they are heated they arev automatically dropped'to the bottom of the furnace, where they can be used at will.` y

Should, for Aany reason, the arc go out,

the relay 11 instantly responds, closing a circuit by wa" .of the contacts 13 through the shunt holdyi tains the electromagnet\4 energized, thereby holding the work in position to be heated by the are, after it has beeV '/reestablished.

In certain forms of o ,r furnace the-shunt electromagnet winding 12 and the relay 11 may be dispensed with by providing a tilting means for the furnace. Such an arrangement as this is shown in Fig. 4 in ngcoil 12, which still mainjon# which the body 1 iscarried on journals 14 supported by any suitable manner such asK end brackets I15 which form part of the framework carrying the furnace. It is to be understood, of course, that a combinationv of the magnetholding means and tilting arrangement, as shown for example in Fig. 4, may be used. In the form shown in Figs.

4 to'. 7 inc. the back wall of the furnace is inclined `at an angle at the'portion carrying the electromagnet 4. The object of inclining the'wall at this point is to provide some friction for the work, whereby the friction serves to vary the flow ofthe rlvets or Work.

'In this particular form of furnace a cover -16 is shown closing the opening 2 and a cover 17 isshown closing the opening `8. Also four electrodes are illustrated for heat. ing the furnace, an extra air 18 and 19 being used as illustrated dlagrammatically in Fig. 9. 'Otherwise this furnace functions in a similarinanner to that illustrated in In Fig. 10 which is the rcuit diagram 3, two, relays balancingv resistanoes 36 an l11 are 'utilized and they electromagnet4 cari.

2() is separated 'from the work chamber 3 by means 'of-a baie'wall 21. The wall 21 serv-J ing to throw the heat upward vagainst, the

work. The electromagnet 4 has a somewhatdifferent form as illustrated. A circuit ari i rangement for the type of furnace shown in Figs. 11 to in Fig. 8.

In V, Fig. 14 'we have illustrated' an end view f a further. Amodified form of the furnace embodying our invention, more details "beingshow'n in this form' than in the. others previously described; for example, the covering 16 for the opening 2 is shown in' the form of a door having a handle 22,

l hinges`23and a catch 24 for holding the 'door 1'6 in position. Also the cover 17 has hinges and a catch similar to the door 16., The furnace in this form is supported on journals 14, the same ,as the furnace shown 1n Fig. 4, but a ratchet. wheel 25 and a catch '26 is providedjto holdl the furnace in any desired tilted position. It is-to be underlstood, of course, ythat similar devices may used on the rnaces previously described to hold them in any desired ition, whereby the time of the falling o lthe work awa from the electromagnet may be controlle It 'may also be mentioned at this^point that the flow of the rivets o-r work may be further controlled by adjusting the strengthfof the that any7 suitable feeding means electromagnet 4 in any well known m nner.

Figures 14, 15 `and 16 alsoillustrate one means of supporting and feeding the electrodes fand 6, but itis to be understood eitherautomatic or manual may be provided.v In this form of furnace we haveprovided a somewhat diierent type of heating chamber and lwe have shown a larger passage too for loading the furnacefwith rivets.v We' hayef also shown the rivets directly on the auxiliary heater, after theyhave been dropped by theelectromagnet. The circuitarrangement for this type of furnace is that illustrated in Fig. 19 Vin whichv the holding coil is repre-` sentedlby 10 and the stabilizing resistor by 7 'Theholding coil 10 Amay be energized 'by some 'othersourceof current than that sup-` plying the electrodes`5 and 6- and when so energized, the circuit arrangement of Fig. 20 is used. f

In the 'discussion ofthese furnaces it may be remarked that the` usual source of current 13, inc. may be that illustrated supply is alternatingin character, and in the lfurnaces which we have constructed and tested, wehave utilized alternating ,current forl heating purposes. We-have also used both alternating and direct current on the holding coil, in which case we have utilized ru aizangement similar to that shown in 1 i pecial reference may be made at this point to the stabilizing resistorV 7 as illus-y trated particularly in Figs. 16, 17 and 18. As illustrated in these figures it `is shown as a plate to vwhich contact is made at the ends through the medium of blocks 27 umd.

connectors 28, both preferably of graphite. Blocks 29` preferably of non-conducting material such as iirebrick, are pressed against the connectors` 28 by means of clamps 3() carried on bolts 31 fastened to the ch'annel ends 32 constituting a part of the framework of the furnace. Resilient members. such as springs 33, are utilized pack of the clamping nuts 34. These resili- 'ent members 33 are utilized to take up the expansion and contraction of the plate 7, blocks 27, connectors 28- and blocks '29. Whereby\a satisfactory electricalgcontact is always maintained between the 'connectors' 28. blocks 27 and resistor plate7. The materialcoustituting plate 7 and the vmethod of making the same Willnot be described herein, as it forms no part of bur present invention, but will be made the subject of another application. f

In the form of-furnace shown in Figs. 21 to 24,inc., we have` substituted in place of the\ arc electrodes l5v and 6 a heating device`35, which is similar to thestabilizing resistor 7 holding the rivets on the plate 35 by means. of the electromagnet 4, which in these fourviews 2l1to 24, inc., is of a somewhat different formfthan that previously described. In these latter forms we may use direct current' of suitable voltage' on the magnet. Itl will b e noted in this latter form that Lthe furnace can be tilted for the purpose of rolling thel work back onto the `plate 35, incase it is desired or-.in ca se the 'electremagnet 4 .is dispensed with. yIn'this type of furnace it .will beseenthat the heat derived from the resistor plate 7 will rise to the top plate of the furnace a d lassist .the'plate 35 in heating the rivets. fr,

'In the form shown in Figs.'25 to 27, inc., the furnace is made` substantially rec'tangue lar in shape and`rivetsvare heated on both the heating units 7 and .35, the heat from 7 .serving to assist in heating the rivets on plate 35. After the rivets are heated they 'may be manually -moved'from the plate 35 to the plate 7. which is ata-somewhat lower heat, or the furnace may be tilted asin the other forms describd,ca sing the work on Athc top plate to pass to e bottom one and when the furnace is tiltedfb'ackto-normal position the vork will be spreadout ion the ottoni plate. `r`The method of making con- .nection'to the plates 7 .and 35 is illustrated in Fig.'27 and more in detail in Fig. 2B and is very -similar to the -method already described in connectioniwith Fig. 18.l It will be observed that this 'method ,ofclamping' and making connections with the Vspecial heating units 7 and 35 permits these heating units to be easily and quickly replaced when desired. The electrical circuits may be either one ofthe four forms shown in Figs. 29 to 32. -In Fig. 29 a' transformer T is illustrated having a primary P in which the number of turns are adjustable and' a secondary Sconnected to the resistors 7 and y 35, which are shown as being connected in multiple. Figi 30 is the same as Fig. 29` except the resistors 7. and35 are connected in series, While in Fig. v31, the transformer T is shown of a two \phase type, one phase being connected to the v, resistor 7 .and the other to resistor While Fig. 32 shows-a' transformer having a three-phase primary supply with a two phase secondary, one phase being connected toresistor 7 and the other to resistor 35. The arrangement of Figs. 25 to 27, inc.,- gives hot rivets before the furnace is heated up. That is to say, thev plate 7 and 35 are the first to heat and since therivets .are' placedl directly von the plates, they (begin to heat at once; while in other types of furnaces the furnace itself must be heated up more or less before the rivets begin to take up heat.

' It lW-ill vbe observed that in the forms of furnaces herein described in which an electric are, 'or vWhen an electricarc is not used, gas or liquid fuel is used in place thereof, that the cold rivets or Work are' .held in the direct path of the heat raysby means of the magnetic field. In some cases it may be advisable to supply the mama the furnace with gas or oil an keep the b ttoin hot by electric current which maybe thermostatically controlled. A l' Furthermore that the furnace wall is l arched so as to focus heat rays onto the work. Also when the rivets reach a proper heat and before burning occurs, they auto-v matically drop beneath or behind the'region of the arc or direct source of heat, to a-point where the heat is reflected or caused by convection currents, thereby providing automatic protection against the burningof the rivets or Work. l 1

It will be further observed that cold rivets are fed from above and progress throu h the v various stages of heating to a fnishe heat and. arev then automatically conveyed to a convenient place near theexit door, which is beneath the feed door. Also it will beseen that a lconsiderable quantity of rivets or piecesmay be fed in aty one time, so that.v

the number of times the feed door is opened lplace.

back 1n the feed passage are preheated to isredced to a minimum. -In other Words,

lactually filled full of rivctsand as they are heated up `they are automatically released and other rivets or Work falls down in the region of the magnetic field to. take their It will" be observed that/the rivets a considerable extent before they get ,down to the real hot regionconsequently the heat 1n the feed passage is not Wasted.

Besides the advantage of being able to heat a large quantity of rivets of any or different sizes andto ha^ve this supply always on hand, it will lbe seen that the rivets must bev substantially heated uniformly throughout before they are released by the magnetic field, and the further advantagi` of ourl furnace is that it is' very high in electrical and thermal efficiency and we have found that the radiated heat 'from the fura naceis not a discomfort to the operator as in other types of furnaces.

l ln certain of the figures, for instance Figs. l and 2. the resistor 7 is in thel form of a single plate. but the resistor I7mayl be made 'up of a. number of strips. the same as shown in Figs. 7 and 13. in which figures, as Well as in Figs. 'l and 2, the resistor 7 is placed.

lslightly 'below the surface of the bottom of the chamber 3, so that the Work does not make direct electrical contact with the plate or plate sections, which sections may be connected in series or parallel or a combination of the t-Wo if desired. When the resistor 7 is substantially flush With the bottom of the chamber 3 as illustrated in Fig. 16, or when the resistors 7 and 35 are disposed as in Figs. 24 and 27, then We have' found that there is some danger of the electric. currentleaving the resistor 'and passing through the rivets themselves in `multiple paths with ortions of the resistor plate, tending to urn the rivets or work pieces in spots, or even to fuse the pieces of Work together.

In order to overcome this dieulty we have utilized avery thin layer of substantially non-electrical conducting material on the surface of the resistor 7. For the purpose of clarityywe have madeno attempt to show .this electrical non-conducting material o-n the resistor 7 in the figures mentioned. Ve

vhave also overcome this difficulty byuse of laI material Which is somewhat soft, Whereby the work pieces Will imbed themselves slightly in the material, thereby increasing the heating contact and holding thework pieces in ^position so that they are not Aapt to become shifted around and make contact with each other, thereby forming a parallel circuit with aA section ofthe resistor plate, but, as has been" pointed out, lthe material constituting the resistor described herein. v

f As explained, .the drawings are more or will not be further less diagrammatic in form and it will, therefore, be understood to one skilled in this art heating the chamber-and said work to a critical temperature, with further means for vretaining the work in a designated' portion of the chamber untilait has been heated to said critical temperature whereby the Work releases itself and then moves automatically to another part of the furiiace; saidr means for lretaining the Work comprising an eleotromagnet having all its parts located Wholly outside of the chamber and out ofv direct, contact with the work.

2. In a heating furnace including a chamber for the reception of Work, means for,

heating the chamber and said 'Work to a critical temperature, with further meaiisfor retaining the work in a designated portion of the chainberunt 14 it has been heated to said critical temperature, whereby the `work releases itself and then moves automatically to another part of the furnace; said retain- -ing means for the Work comprising an electromagnet so positioned that` all its partsV are self-cooling; and means for varying the 'predetermined vcritical heating temperature'.

.3. In a heating furnace, a chamberl having la' designated portion for the reception'of l work to tbe, heated, means for' producing heat within the chamber `and directingr thesaine toward the Work, means forholding the work Within saiddesignated portion until Aa critical temperature of the Work is reached, whereby the work is automatically released and passed to another part of said furnace lout of the direct rays of said source f of heat, and auxiliary means for sup-plying heat'tothe work at said other part of the furnace for the' purpose described.

4. In a heating furnace, a chamber yfor the reception of work to be heated, electromagnetic means forfretaining the work vin a'designated portion of the chamber until it has been heated to a predetermined teinperature at which point it is Y`automatically released and lpasses to another Jpart of the furnace, means-for varying this predetermined temperature, means for producing heat and directing it onto the work and an auxiliary source of heat in said'other part of the furnace for maintaining the Work in a heated state.

5. In va heating furnace, a chamber having a designated portion for the reception of work to be heated, means for holding the work in said `designated portion until apre- I. determined temperature is reached, and then releasing thework, means for heating said VWork and-chamber, and means for tilting the furnace, whereby any work within the chamber may bey moved to said designated portion for' heating..

6. In a heating Ifurnace having a chamber'with openings therein for Ifeeding in -and withdrawing work therefrom, said chamber having a designated Aportion at whiclithe work is to be heated, means for supplying heat to said chamber and directing it -towards said work, an eleetromagnet for automatically holding said work within said: designated portion until a vpredetermined temperature is reached and then passling it to s-aid withdrawal opening of the furnace, and an auxiliary source of heat for maintaining said Work at substantially said predetermined temperature. v

' 7. In a heating furnace` a chamber having a designated portion for the reception of work to be heated, an electromagnet for holding the work in said designated portion untila ,predetermined temperature is reached, and then releasing the work, said portion 'being so positioned With respect t0 the bottom of said 4furnace thatfwhen the work lis released it will automatically pass to the bottom ol said furnace, are electrodes for heating .said Work andl chamber and means for tilting thevfurnace, whereby any` win-ii on the `bottom'thereof may be 'moved to said designated portion as and for the purpose described.

8. In a heating furnace, a 4chamber having a work feed opening and a withdrawal opening and a portion intermediate said openings for retaining the Work while it is lheilig heated, means for supplying heat and directing it toward said chamber portion and means for retaining the work Within said portion until a predetermined temperature of 'the work is reached whereby it is then automatically passed to that'part of the furnace near said withdrawal opening` said feed opening being pointed itoward said intermediate portion so as to feed the work automatically to said chamber portion as said4 Work is heated and released therefrom, and an auxiliary heating deviie adjacent said Withdrawal opening for the'purpose described.

' 9. In a heating furnace, a chamber having adesignated portion for the reception of work to be heated, an elcctromagnet located wholly outside the furnace for hold- -ing the work in said designated portion until a predetermined temperature is reached and then releasing the work, and an electric arc, liavingits current passing through said eleetromagnet, for heating said work and chamber. l

' 10. In a heating furnace, a chamber having a designated portion for the reception of work to be heated, an electromagnet for holding the Work in said designated portion until a predetermined temperature isv reached and then releasing the work, an' electric arc having its current' passing through said electromagnet for heating said work and chamber, and additional electromagnetic means for'holding 'the work 'in' said furnace portion should said are go out.

11. In a heating' furnace, a Work heatingV chamber, arc electrodes extending within said chamber, av resistor connected in series with said arc electrodes, and an electromagnet having a winding invseries with said are electrodes for` holding the Work in'a position to be heated until a predetermined temperature ofthe work is,reached.

1-2.- In av heating furnace, a.-Work heating chamber, are Aelectrodes `extending within said chamben--a---resistor c'arriedin the bottom `of said lfurnace and connected in series with-said arc electrodes, an electromagnet so positioned on .the furnace. as tol attract saidjworkaas iti-is fed intothe furnace an'd 25yhold lthe-'same until a .predetermined temperatureofthe work is reached, when said Work'l will,'fall automatically over said resistor-femme purpose described.

13.- In a-'heating furnace, a chamber having arc electrodes for heating-work to a predetermined temperature, electromagnetic means for'. holding the work in a given portion of the furnace until said'temperature `is reached..- and then releasing the same, and 85 .a resistor in another portionl of the furnacev for maintaining the Work at near the releasing temperature. l

. 14. In a heating furnace, achamber having means for heating work, introduced 40 therein, to aA predetermined temperature,

means for holdingthe work in a given portion of the furnace until said temperatureis reached; then releasing the sameand passing it to the bottom of the chamber, a re sistor situated in the bottom of said chamber, and means associated with the resistor for preventing the'work pieces from forming a definite electrical shunt path with any substantial portion of said resistor. Y 15. In a heating furnace, a chamber having aportion formed and positioned for the reception of work pieces, means for .holding the work in said portion of-the furnace'ultil .a predeterminedtemperature is reached; then releasing the work pieces, whereby they V fall to the bottom of the furnace, means for heating said work pieces when so held, a resistor constituting a part of the bottom ofl the furnace, means forheating the resistor 69 to maintain the Work pieces hot, and means Y for preventingthe 'work pieces from forming any substantial electrical shunt to a part of the resistor.

i ipasas 16. In' a heating furnace, a chamber having aportion formed and positioned for the reception of' work pieces, electromagnetic means for holding the work in said portion of the furnace until-a predetermined tem"- perature is reached, then releasing the work pieces; whereby they'fallto'the bottom of the furnace, -arc electrodes fory heating the Work pieces when so held, a resistor in series with said electrodes and forming a. part' of the bottom of the furnace,with means associated with the resistor ,for preventrng the-work pieces as they fall to the bottom of the furnace from forming any substantial yelectrical shuntv circuit to a portionqof the resistor.

17. In a heatingrfurnace, la lchamber hav- 80, ing means for heating work to a predetermined automatically releasing temperature in one portion -With means external of the furnace for holding the' work in saidv portion-until such predetermined temperature is reached, and alsecond portion equipped with means for holding-the work at substantially said temperature. i, 18.- In a heating furnace, achamber having .means for heating work` Ito a predetermined automatically releasing temperature in one portionwithl 4means external of the furnace for holdingthe Work in said portion until such 'predetermined temperature is reached, and a second portion equipped with means for holdingthe workat substantially said temperature, .said second mentioned means serving also to heat the chamber and preheat the work as described.

19.1In a heating furnace, afwork heating ,100 chamber having arey electrodes.` therein, a resistor located'in the bottom of the chamberand connected in series with said arc electrodes` an electromagnet having a winding in series with said larc electrodes for the T05 purpose described and quick detachable yielding means for holding said resistor,- in positionin the furnace.

20. In a heating furnace, a chamber having arcelectrodes therein, a supplemental heating device therein connected. in series with said arc electrodes, and quickly detach.V able yieldingl means for holding said heating device in place in ,said chamber.'

'21. In a heating furnace, chamber having are electrodes therein, a re sistor located in the bottom of the chamber and connected in series with said arc electrodes, and an electromagnet having a Winding in series with said arc electrodes for the purpose described.

In'testimony whereof, -we have hereuntov put our' signatures, this 16th day of January, 1922.

1 THOMAS M. HUNTER.- CLAUDE J .IIOLSL G a workheating 

